The present invention relates generally to an electronic lock device for locking and unlocking a door by way of a preset code entered via a keyboard with a plurality of push buttons. More particularly, the invention relates to a mischief prevention device in the push-button electronic lock device.
In such an electronic lock device, the preset code consists of an encoded sequence of digits, each of which can be entered by depressing a corresponding push button. Such a system can possibly be accidentally and unnecessarily operated to lock or unlock the door by depressing the push buttons at random. This possibility can be reduced by using a rather long preset code since this makes it difficult to enter all of the encoded digits in the correct order. On the other hand, a long sequence of digits is difficult for the user to remember. Alternatively, it is also possible to reduce the possibility of such mischief by providing a relatively large number of push buttons to increase the number of code sequence combinations. However, this makes the lock device more expensive.